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activity of the potent anabolic effectors: insulin-like growth factor-I
(IGF-I) and fibroblast growth factor-2 (FGF-2), play a role in aging
associated muscle loss. The effect of fitness level on IGF-I and FGF-2
responses to all-out anaerobic exercise in older men was studied.
Twenty four healthy older males: 12 higher fit (58 ± 1y) and 12 lower
fit (59 ± 1y) underwent the Wingate anaerobic test. Serum levels of
IGF-I and FGF-2 were measured before, immediately after exercise,
and 50 min into recovery. Immediately post exercise, the average peak
power output and serum lactate were higher (p < 0.05) in the higher
fit (446.0 ± 14. 9 kgm·min-1 for mean (± SD) peak power
and 12.6 ± 1.1 mml·l-1 for lactate) compared with the lower
fit individuals (284.0 ± 6.5 kgm·min-1 and 8.5 ± 0.7 mml·l-1,
respectively). Pre-exercise IGF-I was lower and FGF-2 was higher in
the higher fit (335.0 ± 54.0 ng·ml-1 and 1.6 ± 0.1 ng·ml-1,
respectively) compared with lower fit individuals (402.0 ± 50.0 ng·ml-1
and 1.4 ± 0.2 ng·ml-1, respectively). Following the anaerobic
exercise, in both groups, FGF-2 decreased dramatically (p < 0.05);
in the higher fit individuals FGF-2 level was 0.4 ± 0.1 pg·ml-1
compared to 0.1 ± 0.02 pg·ml-1 in the lower fit individuals.
In contrast to FGF-2, IGF-I increased transiently to levels of 405.0
± 62.0 ng·ml-1 in the higher fit individuals and to levels
of 436 ± 57.0 ng·ml-1 in the lower fit individuals. However,
the IGF-I elevation was significant (p < 0. 05) only in the higher
fit individuals. In conclusion, the present study demonstrates that
during aging, fitness level can alter circulating levels of IGF-I
and FGF-2. Furthermore, fitness level can affect the response of both
mediators to all-out anaerobic exercise.
KEY
WORDS: Anaerobic exercise, aging, growth factors; hypertrophy,
angiogenesis.
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